Ok, so what the anti-virus was picking up was a remnant from an infection we had a while back. Before you guys head for the pitchforks, the page that contained the payload has been long gone since we cleaned up that infection. It looks like we missed some error pages that pointed to that page (in an iframe). It appears Avast was throwing errors because the iframe looked suspicious and matched the way a virus is transmitted.
tl;dr version:
You shouldn't see the warning anymore. It wasn't an actual virus, just a cautious warning by the antivirus.
